Batteries can be broadly classified into primary and secondary batteries. Primary batteries, also referred to as disposable batteries, are intended to be used until depleted, after which they are simply replaced with one or more new batteries. Secondary batteries, more commonly referred to as rechargeable batteries, are capable of being repeatedly recharged and reused, therefore offering economic, environmental and ease-of-use benefits compared to a disposable battery.
Although rechargeable batteries provide a much longer service life than disposable batteries, their service life is not unlimited. Depending upon the type of battery, a rechargeable battery can typically be recharged anywhere from 100 times (e.g., alkaline) to 1000 times (e.g., lithium-ion, lithium-polymer) to 20,000 times or more (e.g., thin film lithium). In addition to depending upon the type of battery chemistry involved, the number of cycles that a rechargeable battery can be recharged depends on a variety of other factors that include; (i) the rate of charging (i.e., slow trickle charge versus fast charge), (ii) the level of charging (i.e., 75% of full charge, full charge, over-charged, etc.), (iii) the level of discharge prior to charging (i.e., completely depleted, still charged to a low level, etc.), (iv) the storage temperature of the battery during non-use, and (v) the temperature of the battery during use.
Due to the high initial cost of rechargeable batteries, expensive products such as laptop computers often incorporate relatively sophisticated power management systems, thereby extending battery life and allowing the use of smaller, lower capacity batteries and/or batteries that utilize less expensive cell chemistries. One of the most common power management techniques is to place certain laptop components and peripherals, especially those that require relatively high levels of power to function, into either a standby mode or a low power usage mode whenever possible. Thus, for example, a laptop may provide two different video screen brightness levels; high brightness when the computer is plugged in, and low brightness when the computer is operating on battery power. This is also the primary purpose behind powering down the video screen when the computer is inactive for more than a short period of time or placing wireless connectivity capabilities (e.g., Bluetooth, WiFi, WAN, etc.) or other non-essential peripherals in standby mode when they are not required.
A growing application for rechargeable batteries is that of electric vehicles. All-electric and hybrid vehicles, however, present a number of engineering challenges, primarily due to the need for the rechargeable battery pack of such a vehicle to meet the consumers' expectations relative to performance, range, reliability, lifetime and cost. The present invention provides a battery pack management system that helps achieve these goals.